The present invention relates to an automatic cutting liquid supply apparatus in which the amount of cutting liquid that is supplied to each of various types of tools used in a machine tool such as a machining center, etc. is automatically supplied in accordance with predetermined optimal supply conditions that include variations over time during operation.
Various types of conventional cutting liquid supply apparatuses exist. In, for instance, Japanese Patent No. 2687110, xe2x80x9cMain Shaft Device for Machine Tool,xe2x80x9d an NC type machine tool equipped with a minimum-quantity cutting liquid supply (MQL) system is disclosed. In this prior art, two supply paths that supply a gas and a liquid separately to the inside of the main shaft of a machine tool are provided; and a mist generating device, which mixes the gas and liquid supplied via the supply paths and sprays the mist formed by this mixture, is installed inside the tip end portion of the main shaft or inside the tool holder.
Japanese Patent Application No. H11-112601, xe2x80x9cCutting Liquid Supply Apparatus for Machine Toolxe2x80x9d discloses a conventional cutting liquid supply apparatus. This cutting liquid supply apparatus is used in a machine tool in which a cutting liquid is supplied to a mist generating device that is provided in the tip end portion of the main shaft from a cutting liquid supply pump via a cutting liquid supply line. The machine tool is equipped with a cutting liquid absorbing and discharging means which absorbs a fixed amount of cutting liquid inside the cutting liquid supply line when the cutting liquid supply of the cutting liquid supply pump is stopped and supplies a fixed amount of cutting liquid to the cutting liquid supply line when the cutting liquid supply of the cutting liquid supply pump is initiated. Thus, this is an NC type machine tool equipped with a minimum-quantity cutting liquid supply (MQL) system.
Among the conventional cutting liquid supply apparatuses, further, the apparatus in Japanese Patent No. 2687110 and the apparatus of its improvement in Japanese Patent Application No. H11-112601 are respectively provided with a mist generating device and a cutting liquid absorbing and discharging means. These apparatuses are further equipped with a minimum-quantity cutting liquid supply (MQL) system. However, in both apparatuses, cutting liquid at a fixed pressure is merely supplied to the cutting tool over time from the cutting liquid supply means. Accordingly, optimal supply conditions including variations in the amount of cutting liquid supplied over time during the operation of the machine cannot be ensured. For example, the supply conditions that correspond to variations over time during operation, such as the initial operating time (TI) during which the working operation is initiated, and the subsequent constant operating time (TC), etc. depends on whether the tools are those that are used for the first time or those that have a history of previous use. Thus, there is difficulty in the presetting and automatic maintenance of various types of optimal supply conditions (including variations over time during operation) for the cutting liquid supply quantity (Q) that is supplied to each of the tools.
In conventional cutting liquid supply apparatuses, though the minimum-quantity cutting liquid supply (MQL) system is employed, it is still difficult to preset and automatically maintain various types of optimal supply conditions (including variations over time during operation). Accordingly, it is not easy to obtain good cutting characteristics. In addition, a long tool life cannot be ensured, and wasted cutting liquid is expended. It is thus difficult to ensure a so-called completely dry cutting system that is environmentally friendly.
In order to solve the above-described problems, the automatic cutting liquid supply apparatus of the present invention is characterized in that a variable frequency generating means for generating an output frequency signal (F) that corresponds to the input signal (Vin) is used so that a cutting liquid supply quantity (Q) that is proportional to the output frequency signal (F) is supplied to a tool from a supply pump.